> For the complete documentation index, see [llms.txt](https://docs.talus.network/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.talus.network/concepts/00-protocol-overview.md).

# Protocol Overview

{% hint style="info" %}
**Audience:** Developers and integrators learning Nexus.

**Goal:** Build a connected mental model from an Agent through execution, settlement, discovery, and protocol evolution.
{% endhint %}

Nexus is an on-chain protocol and hosted service boundary for building, running, paying for, and verifying agentic workflows on Sui. The protocol records identities, workflow definitions, execution evidence, and payment state; application developers keep custody of their own business state.

### The protocol story

An **Agent** identifies a reusable set of skills. A **Tool** performs one capability in a workflow, and a **Verifier** describes how the result should be trusted. A **DAG** orders tools and routes their outputs. A **Task** schedules an occurrence of that DAG, and a **Leader** advances eligible work under on-chain authority. Payment state funds and settles the result, while registries resolve the identities involved.

<figure><picture><source srcset="/files/dFVnSQjV1KaF72nwJKzL" media="(prefers-color-scheme: dark)"><img src="https://2322144477-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FlV9L0m4FfiDv8fzxk6cT%2Fuploads%2Fgit-blob-f17a3b72590f63beae63495eb801e0456a279e99%2Fprotocol-overview-light.svg?alt=media" alt="Nexus protocol overview: registries and discovery connect agents, tools, verifier trust, and eligible leaders to DAG execution, payment settlement, and application business state"></picture><figcaption><p>The flow follows discovery, execution, settlement, and the feedback path between the DAG and an eligible Leader.</p></figcaption></figure>

The arc introduces these actors before it explains the registries that make them discoverable. Start with [The Talus Agent](/concepts/01-talus-agent.md), then learn what application state belongs to you in [Assets and Business State](/concepts/02-assets-and-business-state.md).

#### Choose a development surface

* **Guides** teach a task with a verifiable outcome, such as building a TAP, funding an execution, or inspecting on-chain state.
* **Concepts** explain why the protocol has each actor, object, and boundary.
* **Reference** records exact public Move, SDK, CLI, hosted API, and other generated surfaces.

#### Core execution actors

* The **Agent developer** defines the Agent, skills, application state, Tool choices, and payment policy.
* The **Tool developer** publishes an on-chain Move Tool or operates an off-chain Tool endpoint with the declared schema.
* The **caller** creates a Task or occurrence with inputs, timing, funding, and verifier choices.
* The **Leader** observes eligible work, invokes the selected Tool, submits result evidence, and participates in settlement.
* The **protocol state** assigns eligible Leaders and constrains each action by the pinned workflow, Tool, verifier, and payment state.

The Leader description is intentionally public and conceptual. Exact contract signatures remain in the generated [Leader reference](/reference/move/nexus_registry/leader.md).

#### Where to continue

1. Understand the identity and skill boundary in [The Talus Agent](/concepts/01-talus-agent.md).
2. Design durable application assets in [Assets and Business State](/concepts/02-assets-and-business-state.md).
3. Learn callable capabilities in [Tools and Skill Packages](/concepts/03-tools-and-skill-packages.md).
4. Choose result trust in [Verifiers and Result Trust](/concepts/04-verifiers-and-result-trust.md).
5. Follow the live run in [DAG and Execution](/concepts/05-workflow-dag-execution.md).


---

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